1. Field of the Invention
The present invention relates to a process for washing a molding die for preparing a casting die (or core), and an apparatus therefor. In particular, the casting die (or core) is prepared by a cold box process.
2. Description of the Related Art
In a cold box process, a mixture of a phenol resin composition and a polisocyanate is compounded with a casting silica sand to prepare a casting sand. The resulting casting sand is filled in a molding die. Then, a TEA (i.e., triethylamine) gas is introduced into the molding die. Accordingly, a polyurethane resin arises to work as a bonding agent. The bonding agent can be cared at an ordinary temperature. Thus, a casting die (or core) can be prepared precisely in accordance with a cavity of the molding die. After molding the casting die by the cold box process, the bonding agent and silica sand reside on a molding surface and in a vent hole. The molding surface forms the cavity, and the vent holes are opened in the molding surface. Consequently, it is necessary to remove the bonding agent and silica sand when another high-quality casting die should be molded by reusing the molding die.
Conventionally, the following 3 washing processes have been employed to wash the molding die:
(a) brushing the molding die with a metallic brush together with an organic solvent; PA1 (b) blowing the molding die with highly pressurized air together with an organic solvent; and PA1 (c) blowing the molding die with shot particles made from glass or stainless steel, or with sand. PA1 a holding unit for holding an opened molding die for a cold box process after usage therein, the molding die including a molding surface; PA1 a reservoir unit for reserving washing water therein; PA1 a heating unit for heating the washing water reserved in the reservoir unit; PA1 a pressurizing unit for pressuring the washing water reserved in the reservoir unit; PA1 a blowing unit or blowing the washing water to the molding surface of the molding die held in the holding unit, the washing water heated at a temperature of 70.degree. C. or more and pressurized to a high pressure of 10 MPa or more, the blowing unit connected with the reservoir unit; PA1 a circulating unit for collecting the washing water after the blowing operation and circulating the washing water to the reservoir unit; and PA1 a filtering unit for filtering the washing water after the blowing operation.
However, it is difficult to remove the bonding agent and silica sand from the molding die by the aforementioned conventional washing processes. Especially, it is difficult to remove them from narrow or congested areas. Accordingly, it is necessary to manually carry out the washing operation by an operator. In addition, it is needed to frequently carry out the removing operation, and it is inevitable that the time required for the operation should be prolonged. Moreover, even if an organic solvent is used in the conventional washing processes, the organic solvent might adversely affect ejector pins, etc., of the molding die, depending on the types of the organic solvent employed.
In particular, the vent hole cannot be processed effectively by the first and second conventional washing processes (a) and (b). Even if the vent holes are processed by the third convention al washing process (c), the molding surface around the vent hole might be damaged, and a mesh, which is usually provided for the vent hole, might be damaged. Moreover, the mesh might make it difficult to recover the glass particles, etc. Consequently, the mesh, etc., should be replaced with new ones regularly under the current circumstances.